From f265ae8c79ce8c194de481e9def1daa3a80dbb96 Mon Sep 17 00:00:00 2001 From: Alistair Francis Date: Mon, 27 Jun 2016 15:37:32 +0100 Subject: [PATCH] cadence_gem: Avoid infinite loops with a misconfigured buffer A guest can write zero to the DMACFG resulting in an infinite loop when it reaches the while(bytes_to_copy) loop. To avoid this issue enforce a minimum size for the RX buffer. Hardware does not have this enforcement and relies on the guest to set a non-zero value. Signed-off-by: Alistair Francis Reported-by: Li Qiang Reported-by: P J P Message-id: 84bb1c391b833275da3f573d4972920cea34c188.1466539342.git.alistair.francis@xilinx.com Signed-off-by: Peter Maydell --- hw/net/cadence_gem.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/hw/net/cadence_gem.c b/hw/net/cadence_gem.c index 0346f3e335..e5f3c985a4 100644 --- a/hw/net/cadence_gem.c +++ b/hw/net/cadence_gem.c @@ -664,6 +664,13 @@ static ssize_t gem_receive(NetClientState *nc, const uint8_t *buf, size_t size) GEM_DMACFG_RBUFSZ_S) * GEM_DMACFG_RBUFSZ_MUL; bytes_to_copy = size; + /* Hardware allows a zero value here but warns against it. To avoid QEMU + * indefinite loops we enforce a minimum value here + */ + if (rxbufsize < GEM_DMACFG_RBUFSZ_MUL) { + rxbufsize = GEM_DMACFG_RBUFSZ_MUL; + } + /* Pad to minimum length. Assume FCS field is stripped, logic * below will increment it to the real minimum of 64 when * not FCS stripping -- GitLab